The ignition device for an internal combustion engine (hereinafter referred to as the ignition device) disclosed in Patent Literature 1 or the like has been increasingly reduced in size. This type of ignition device includes: a switching element applying or interrupting current flow in an ignition coil (i.e., load); and a control IC driving the switching element to turn on or off in response to an ignition signal (i.e., input signal) as a rectangular wave inputted from an engine ECU (i.e., electronic control device).
Since a high-frequency/high-voltage surge resulting from electrostatic discharge (i.e., ESD) may be applied to an input line (i.e., a signal input line) for the ignition signal, a surge protection circuit is provided in the input line. In addition, the measures against AC noise induced in the signal input line are also needed. Accordingly, as a circuit configured to protect the control IC from a negative surge and clamp the negative voltage of the AC noise, a diode connected between the signal input line and a ground line and having a cathode connected to the signal input line is used. The diode can be embedded in the control IC.